The software that has no restrictions from copyright holder regarding modification of the software's internal and its redistribution is called an Open source software. They are being provided for use and redistribution for free, with no cost. They can be easily downloaded on the Internet.
Without system software, system can not run on the other hand without application software, system always runs
Answer:
3 years of study - Bachelor's degree
2 years of research - Master's degree
3 years of research to earn a PhD
So, On total it would take 8 years!